A patient presents with a vaginal discharge that has a fishy odor and a wet mount examination reveals white blood cells and stippled epithelial cells. What is the treatment of choice?

The presence of a vaginal discharge that has a fishy odor, along with the findings of stippled epithelial cells on a wet mount examination, strongly suggests a diagnosis of bacterial vaginosis (BV). The stippled epithelial cells, often referred to as "clue cells," are characteristic of this condition, which occurs due to an imbalance in the normal vaginal flora.

The treatment of choice for bacterial vaginosis is metronidazole. This medication effectively targets the anaerobic bacteria that often overgrow in BV, helping to restore the normal balance of flora in the vagina. Metronidazole can be administered orally or as a topical gel, and it has been well-studied as an effective treatment for this specific condition.

Other options listed do not effectively address the underlying issue of bacterial vaginosis. Nonoxynol-9 is a spermicidal lubricant that is not used for treating infections. Ceftriaxone is an antibiotic effective for treating gonorrhea but is not indicated for bacterial vaginosis. Clotrimazole, an antifungal, is used for treating yeast infections and would not be effective against the bacterial cause of BV. Therefore, metronidazole is the most appropriate choice for treating this condition.